Field of Art
This disclosure generally relates to data transmission, and, more particularly, to bidirectional transmission of Universal Serial Bus (USB) data using an Audio/Video (A/V) channel.
Background
High-Definition Multimedia Interface (HDMI) and Mobile High-Definition Link (MHL) were designed to transfer uncompressed video and audio content from source devices to sink devices. The uncompressed video provides high video quality as long as the link (e.g., Transition Minimized Differential Signaling (TMDS) micro-USB) can support the full bandwidth and latency needed. Recent changes in popular display technology have made it desirable to transmit HDMI or MHL data over USB enabled devices.
However, it is difficult to simultaneously transfer high resolution HDMI or MHL videos and USB data over USB links due to different bandwidth and latency requirements and limitations associated with USB, HDMI and MHL standards. Bandwidth for audio/video transmission becomes restrictive when USB data is transmitted along the same link. USB data requires narrow latency constraints while audio/video is latency insensitive. Digital video standards, such as HDMI and MHL do not provide synchronous mechanisms for bidirectional USB data exchange between a source device and a sink device.
Additionally, transmitting both A/V and USB over an auxiliary bus of a USB link does not meet the speed requirements of A/V or USB standards. Further, the requirements necessary for high speed transmission of HDMI or MHL across the auxiliary bus leaves the data susceptible to electro-magnetic interference and thus data corruption.